MySQL Workbench Error 1452 suddenly stopped working

Question

I have 2 tables (customers and cars with FK) and in the beginning everything was OK, I was able to insert data until ID 7 and then all of a sudden it just stopped working and gave me an error 1452. Tried to search for solution but nothing helped. Error Code: 1452. Cannot add or update a child row: a foreign key constraint fails (`test`.`cars`, CONSTRAINT `personid` FOREIGN KEY (`id`) REFERENCES `customer` (`id`))

So here are the tables:

CREATE TABLE `customer` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `lastname` varchar(45) NOT NULL,
  `firstname` varchar(45) NOT NULL,
  `city` varchar(45) NOT NULL,
  `age` varchar(45) NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `id_UNIQUE` (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=14 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci

and

CREATE TABLE `cars` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `brand` varchar(45) NOT NULL,
  `model` varchar(45) NOT NULL,
  `reg` varchar(45) NOT NULL,
  `personid` int(11) NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `id_UNIQUE` (`id`),
  CONSTRAINT `personid` FOREIGN KEY (`id`) REFERENCES `customer` (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=30 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci

Answer 1

I think I found the problem and solution (kind of).

Updating an existing AUTO_INCREMENT column value also resets the AUTO_INCREMENT sequence.

So it stopped automatically assigning id to cars table and it worked only if I add id manually. Then I did this: ALTER TABLE tbl AUTO_INCREMENT = 12; and seems to be working now. But still don't know how it stopped working and can't remember to have updated existing AUTO_INCREMENT. Anyway leaving this as an answer.